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What do organisms need to remove
CO2, O2, urea, ammonia and excess heat
What do organisms need from the environment
Glucose, amino acids, fatty acids, water, minerals, vitamins, O2, CO2
Describe the consequence of an organism getting larger
The SA:Vol ratio decreases
Why would a land-living organism not be likely to use its entire surface area for gas exchange
Water would be able to leave the body into the environment
How should whole organisms be described in terms of this unit
With their SA:Vol ratio
How should an exchange surface be described in terms of this unit
By it’s surface area
Why do small organisms have a larger SA:Vol ratio
Because as size increases, volume increases disproportionately
Describe features of small organisms relevant for diffusion
Diffusion distance is short, SA:Vol ratio is large, whole surface can be used for exchange
How short is a suitable diffusion distance
0.5mm
Describe features of large organisms relevant for diffusion
Diffusion distance is too large, SA:Vol ratio is insufficient, demand for nutrients and waste removal is too big
Why are logarithms used as graph scales
To compare things with large variation
What is needed to meet demand
A specialised exchange surface and an efficient transport system to deliver to and from the exchange surface
What do good exchange surfaces include
A large surface area, a short diffusion distance, a large concentration gradient to remove and deliver substance
What is the formula for the surface area of a sphere
4PiR²
What is the formula for the volume of a sphere
4/3 PiR³
Note 
Flashcard (38)